الفهرس 
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Abstract
The present work deals mainly with the petrography, mineral chemistry and geochemistry of the granitoid rocks and their country metagabbro-diorite complex exposed at Gabal Ri Al Jarra (GRJ) area, central Eastern Desert, Egypt.
Gabal Ri Al Jarra (GRJ) area lies in the midway of Qena-Safaga road in the central part of the Eastern Desert of Egypt (Fig.1.1). It is located among Gabal Al Gidami from the west and Gabal Simna from the east, Gabal Umm Saykat from the north and Gabal Eradiyah from the south. The area covers about 275 Km2 that bounded by the following co-ordinates.
Longitudes 33 22` 00`` and 33 30` 00`` E, and
Latitudes 26 22` 00`` and 26 30` 00`` N.
Regionally, the rock units exposed in the investigated area comprise arc metavolcanics, intrusive gabbros, older granitoids, younger granites and dyke swarms arranged from the oldest. Gabbro-diorite rocks form syn- to late-tectonic intrusion with respect to the calc-alkaline metavolcanics and ophiolites. They range in composition from hornblende-gabbro to quartz-diorite. Generally these rocks are associated with the arc type granitoids group (G1 granitoid). In some parts they show diorite to quartz diorite composition. Sometimes, the latter rocks occur as pockets within gabbroic rocks. Two granitic batholiths are exposed in the area which elongated in NNW direction. The older granitoids of study area are highly eroded and weathered forming spherical exfoliation and cavernous features. They are usually friable, medium to coarse-grained, mostly granodiorite in composition. Generally, the rocks are intruded by alkali granites with sharp intrusive contact.